Multiple studies have now confirmed a dramatic link between the health of our microbiome—the trillions of bacteria that live in our digestive tract—and our likelihood of getting devastating viral illnesses like COVID-19. Low-fiber diets, limited exposure to nature, and overzealous use of pharmaceuticals have messed up our microbiome, making many of us more susceptible to viruses than we naturally should be. But the good news is that unlike our genes, our microbiome is constantly evolving, offering a pathway back to health for those who are suffering, and proven protection for those who want to stay well. In this book, Dr. Robynne Chutkan explains this groundbreaking research and offers a prescriptive plan for anyone trying to avoid or recover from a viral illness to rehab their gut microbes and restore their health.